Age Calculator
Find exact age in years, months, and days from a birth date. Your work stays on this device whenever possible.
How to use Age Calculator
- Choose your Birth date with the date picker; the As of date field is prefilled with today.
- To measure age at a past or future point, such as a school cut-off day, change the As of date.
- Press "Calculate age" to get completed years, months and days in one line.
- Read the second line for the total number of days between the two dates.
- If an error appears, check that the As of date is not earlier than the birth date.
Worked example
Set Birth date to 1990-03-15 and As of date to 2024-06-10. Years: 2024 − 1990 = 34. Months: 5 − 2 = 3, but the day difference 10 − 15 is −5, so one month is borrowed and 31 days (May) are added, giving 2 months and 26 days. The result is 34 years, 2 months, 26 days and 12,506 total days.
When to use this tool
- Confirming a child's exact age on a school enrollment cut-off date.
- Working out the age someone will be on a specific future date for an event or policy.
- Getting a precise day count since a birth date for a milestone record.
Important limitations
Age is computed based on local browser calendar dates. It reflects elapsed civil calendar intervals rather than fractional astronomical years.
Frequently asked questions
How are the leftover months and days worked out?
The tool subtracts year, month and day separately. When the day part is negative it borrows the length of the month before the As of date, so results near month ends can differ by a day from other conventions.
Does it handle leap years?
The total-day figure counts every real calendar day, including 29 February, because it measures the gap between two dates. Someone born on 29 February will see a shifted day count in common years.
Can I calculate the age at a future date?
Yes. Change As of date to any later day and you get the age the person will be then, useful for eligibility checks. Only an As of date before the birth date is rejected.
Does time of day or time zone matter?
No. Both dates are read at noon local time, which avoids daylight-saving shifts, so only the calendar dates count. Birth hour and the person's time zone at birth are not considered.
Why does the total-day figure not equal years times 365?
Years vary between 365 and 366 days, and months differ in length, so the exact day count is measured directly. That is why it is a better measure than multiplying the age in years.